This invention discloses a bend insensitive single mode
fiber, which is composed by a bare
glass fiber with a round cross section and two resin protective
layers with circular cross sections surrounding the outer of the bare
glass fiber. It is characterized in that the bare
glass fiber is composed by a core layer with a round cross section and two claddings with circular cross sections. The
refractive index of the core layer is higher than the index of the two claddings and the
refractive index difference between the core layer and the first cladding is larger than the difference between the first and second claddings. The second cladding is made of pure SiO2. The
refractive index profile of the core layer follows a power function, and the
refractive index profile of the two claddings follow a ladder-
type distribution. The loss of the invented
fiber is insensitive to the bending of the
fiber, which meets the requirements of ITU.T G.657.A and G.657.B standards, respectively. It is applicable to the
Fiber To The Home (FTTH) and other
local area network and the
access network systems.